I have written a small demo (tested in GCC 4.6) showing how to get compile-time hashing of a string literal in C++0x.

(Note that the blog is having a little bit of fun with the formatting of the code below; my apologies.)

#include

// NOTE: hashing algorithm used is FNV-1a

// FNV-1a constants
static constexpr unsigned long long basis = 14695981039346656037ULL;
static constexpr unsigned long long prime = 1099511628211ULL;

// compile-time hash helper function
constexpr unsigned long long hash_one(char c, const char* remain, unsigned long long value)
{
return c == 0 ? value : hash_one(remain[0], remain + 1, (value ^ c) * prime);
}

// compile-time hash
constexpr unsigned long long hash(const char* str)
{
return hash_one(str[0], str + 1, basis);
}

// run-time hash
unsigned long long hash_rt(const char* str)
{
unsigned long long hash = basis;
while (*str != 0) {
hash ^= str[0];
hash *= prime;
++str;
}
return hash;
}

// ensure that the constexpr value is really compile-time constant
template
struct test_const
{
static const unsigned long long value = NUM;
};

// test
int main()
{
constexpr unsigned long long value = test_const<hash ("hello, world!")>::value;
unsigned long long value_rt = hash_rt("hello, world!");

std::cout < < "hash =    " << value << std::endl;
std::cout << "hash_rt = " << value_rt << std::endl;

return value == value_rt ? 0 : 127;

}

The code is available at GitHub as well, as will be any future updates/tweaks I make for the demo.